A new genus and species of small characid (Ostariophysi, Characidae) from the upper río Bermejo basin, northwestern Argentina

2004·6.6 MB·English

by  J M Mirande

Revue suisse de Zoologie 111 (4): 715-728; décembre 2004
A new genus and species ofsmall characid
(Ostariophysi, Characidae) from the upper rio Bermejo basin,
northwestern Argentina
Juan Marcos MIRANDE1 Gaston AGUILERA1 & Maria de las Mercedes
,
AZPELICUETA2
1Fundacion Miguel Lillo, Miguel Lillo 251, 4000Tucumân,Argentina.
E-mail: [email protected].
2Division ZoologiaVertebrados, Facultad de Ciencias Naturales y Museo, Paseo del
Bosque, 1900 La Plata,Argentina.
E-mail: [email protected]
A new genus and species ofsmall characid (Ostariophysi, Characidae)
from the upper rio Bermejo basin, northwestern Argentina. - A new
genus and species of small characid is described in this paper. The new
genus, Nans gen. n., is diagnosed by the combination of: ii,7-8 dorsal-fin
rays, 10-15 branched anal-fin rays, 5 teeth in the inner premaxillary row,
rotation of the pelvic bone about 90°, rotation of the pelvic fin muscles,
pelvic fin curved and forming a complete tube in mature males, incomplete
foramen forexit ofthe olfactory nerve in the lateral ethmoid. Other charac-
ters which help in the identification of Nans are the large subcircular
foramen in the dorsal vomerine lamella which articulates with the meseth-
moid, the absence ofan extrascapularsensory canal in thepostemporal, and
a laterosensory canal in the anguloarticular. The type species, Nans inde-
fessus sp. n. was collected in the rio Anta Muerta and arroyo Colorado,
tributaries of the rio Blanco, and in the rio Pescado, upper rio Bermejo
basin, Salta, Argentina.
Keywords: Characiformes - Characidae - Nans - new genus - rio Bermejo
basin.
INTRODUCTION
The rio Bermejo originates in northwestern Argentina and southern Bolivia,
forming the political limit between both countries; it flows into the rio Paraguay after
1,450 km. The fishes ofthe upper rio Bermejo basin were almost unknown until few
years ago. Fowler (1940) published a list about the ichthyofauna of the rio Lipeo,
including 14 species, four ofthem new for science. More recently, Fernandez (1999)
cited 23 fish species found in the National ParkTariquia, southern Bolivia.
In a recent exploration of some rivers and streams of the upper rio Bermejo
&
basin, the first and second authors collected 31 species offishes (Mirande Aguilera,
Manuscriptaccepted 26.05.2004
716 J- M. MIRANDEETAL.
in prep.), including specimens ofan unknown species. The possession ofseveral dis-
tinctive characters excludes this species from other nominal genera of characids. We
describe it as anew genus and a new species.
MATERIALAND METHODS
Measurements are straight distances taken with caliper to the nearest 0.1 mm.
Measurements are expressed as percentages of SL or the indicated length. Peduncle
lengthwasmeasuredfromtheinsertionoftheposteriormostanal-finraytothehypural
joint. Some specimens examined in this study were cleared and counterstained (C&S)
following Taylor & Van Dyke (1985). Vertebrae counts include the four vertebrae of
theWeberian apparatus and the caudal CP1+U1 as one element. Material is deposited
in the following collections: Asociación Ictiológica, La Plata (AI); Facultad de
Ciencias Naturales y Museo, LaPlata (MLP); Facultad de Ciencias, Sección Genètica,
Montevideo (MVD-SG); Fundación Miguel Lillo, Tucumân (CI-FML); Museo de
Ciencias Naturales de Salta (MCNi), and Museum d'histoire naturelle de Genève,
Switzerland (MHNG).
Comparative material (SLin mm). Acrobrycon tarijae: CI-FML 3270, 1 ex., 66.6 mm,
Argentina, Salta, Orân, LaBambù, rio Bermejobasin, rio Blanco.Aphyocharaxparaguayensis:
AI 142, 2 ex. C&S, 18.6-23.3 mm,Argentina, Formosa, flood plain ofrio Bermejo, in Reserva
EcològicaElBaguai.Astyanaxeigenmanniorum:ANSP21627,paratypes, 2ex.,42.5-49.4mm,
Brazil,RioGrandedoSul.Astyanaxlatens:AI 112,2ex. C&S,41.0-45.0mm,Argentina, Salta,
Orân, arroyoElOculto.Astyanaxlineatus: CI-FML3272,3ex.,35.3-72.1 mm,Argentina, Salta,
Orân, La Bambù, rio Bermejo basin, rio Bianco. Astyanax tupi: AI 128, 4 ex., 60.8-70.0 mm,
Argentina, Misiones, Parana basin, arroyo Cunapirù Chico. Bryconamericus agna: FML3700,
holotype, 61.5 mm,Argentina, Misiones, arroyo Tabay, Parana basin;AI 141, 1 ex. C&S, 60.0
mm,Argentina, Misiones, Paranabasin, arroyoTabay. Bryconamericus iheringii: AI 116, 3 ex.
C&S, 39.9-44.3 mm, Brazil, Rio Grande do Sul, Sào Lourenço do Sul, arroios Pinto e Viùva
Teresa. Bryconamericus thomasi: CI-FML 1969, 94 ex. (2 males, 3 females measured), 40.3-
55.4 mm,Argentina, Salta, rio Piedras. Bryconamericus exodon: MLP 18-IX-80-1, 2 ex., 39.0-
43.5mm,Argentina, BuenosAires,riode laPlatainPuntaLara. Characidiumsp.:AI 153, 1 ex.
C&S, 29.6mm,Argentina, Misiones, arroyoZaimânnearitsmouth. Cheirodon interruptus: CI-
FML 3825, 2 ex. C&S, 32.9-33.4 mm,Argentina, Santiago del Estero, Embalse rio Hondo; AI
160, 1 ex. C&S, 34.0 mm,Argentina, BuenosAires, MarChiquitacoastal lagoon. Ctenobrycon
alleni: MLP 6774, 5 ex., 50.0-64.2 mm, Argentina, Santa Fe, laguna Setùbal. Cyanocharax
alburnus: MVD-SG 59, 1 ex. C&S, 42.5 mm, Uruguay, rio Yaguarón in Paso Centurion.
Diapoma speculiferum: AI 151, 1 ex. C&S, 42.6 mm, Brazil, Rio Grande do Sul, Barra de
Ribeiro, Açude dos Garcia. Gymnocharacinus bergi: AI 143, 1 ex. C&S, 52.4 mm, Argentina,
rioNegro, arroyoValcheta. Gymnocorymbusternetzi: CI-FML3826, 2ex. C&S, 33.7-35.6mm,
Paraguay,AltoParaguay,FortinPatria,rioNegro.Hemigrammusulreyi:AI 161, 1ex.C&S,34.2
mm, Argentina, Misiones, Nemesio Parma, rio Parana. Hemigrammus erythrozonus: CI-FML
3827, 2 ex. C&S, 25.5-26.9 mm, aquarium specimen. Hyphessobrycon boulengeri: MVD-SG
122, 1 ex.C&S,38.1 mm,Uruguay,Rocha,rioYaguarón.Hyphessobryconmeridionalis:AI 145,
2ex.C&S,26.5-32.0mm,Argentina,BuenosAires,Berazategui,lagodelParquePereyraIraola.
Hypobrycon maromba: AI 140, 3 ex., 45.5-47.5 mm, Brazil, Santa Catarina, Concordia, rio
Jacutinga. Hypobiyconpoi: MLP9573, holotype, 50.5 mm, Argentina, Misiones, arroyo Once
Vueltas. 1 ex. C&S,45.5 mm,Argentina,Misiones, arroyoOnceVueltas.Markiananigripinnis:
AI 144, 1 ex. C&S, 71.0 mm, Argentina, Formosa, flood plain of rio Bermejo, in Reserva
Ecològica El Baguai. Mimagoniates inequalis: MVD-SG 119, 1 ex., 30.0 mm, Uruguay,
DepartamentoRocha, environmentsclosetoLagunaCastillos.Moenkhausiacf. intermedia: CI-
FML3257, 60ex. (5 measured), 20.1-31.5 mm,Argentina, Salta, Orân, LaBambù, rioBermejo
basin, arroyo El Oculto. Moenkhausia sanctaefilomenae: AI 158, 1 ex. C&S, 31.7 mm,
Argentina,Misiones,rioParananearPosadas. Odontostilbemicrocephala: CI-FML3369, 2ex.,
NEWGENUSAND SPECIES OFCHARACIDAE 717
48.2-51.6 mm, Argentina, Salta, La Bambù, rio Bermejo basin, rio Blanco. Odontostilbe
pequira: CI-FML3451, 1 ex., 31.5 mm,Argentina,Salta,Rivadavia,rioBermejobasin,Pozode
los Yacarés. Oligosarcus bolivianus: CI-FML 3277, 4 ex., 89.8-113.8 mm, Argentina, Salta,
Orân,LaBambù, rioBermejobasin, rioBianco. Poptellaparaguayensis:AI 148, 1 ex., 50mm,
Argentina, Misiones, rio Piray-Mini, in Eldorado. Prionobramaparaguayensis: AI 149, 1 ex.
C&S, 35.5 mm, Argentina, Chaco, flood plain ofrio Tragadero. Psellogrammus kennedyi: AI
150, 2 ex. C&S, 37.4-39.0 mm, Argentina, Formosa, flood plain of rio Bermejo, in Reserva
EcologicaElBaguai.Roeboidesparanensis:AI 155, 1 ex.C&S,39.2mm,Argentina,Corrientes,
rio Riachuelo. Serrapinus microdon: AI 152, 2 ex. C&S, 25.5-29.0 mm, Argentina, Formosa,
flood plain ofrio Bermejo, in Reserva Ecologica El Baguai. Serrasalmus maculatus: CI-FML
3827, 1 ex. C&S, 69.2 mm, Argentina, Salta, La Union, Pozo de los Yacarés, rio Bermejo.
Tetragonopterusargenteus:AI 156,2ex.C&S,55.5-60.0mm,Argentina,Corrientes,floodplain
ofrioRiachuelo. Triportheusparanensis:AI 154, 1 ex.C&S, 129mm,Argentina,BuenosAires,
riode laPiata, inAtalaya.
RESULTS
Nans gen. n.
Type species. Nans indefessus sp. n.
Diagnosis. Nans is anew genus ofsmall characiforms placedwithinthe family
Characidae in light of the absence of characters indicating relationships with other
families of the order. Nans is identified by several probably apomorphic characters:
1-thedorsalfinwithii,7-8rays, 2-therotationofthepelvicboneabout90°; 3-rotation
of the pelvic fin muscles; 4- the pelvic fins curved, forming a tubular structure in
mature males; 5- the incomplete foramen for exit of olfactory nerve in the lateral
ethmoid; 6-thepostemporalwithoutanextrascapularsensorycanal; and7-theabsence
oflatero sensory canal segment in the anguloarticular.
The following characters, which are present in other species ofcharacids, also
help in the identification ofNans, the anal fin with 10-15 branched rays; the reduction
ofsize ofinfraorbitals 2 and 3; the variable infraorbital number, ranging from 4 to 9;
the loss of supraorbital; the short, blunt sphenotic spine; the two rows ofossified gill
rakersontheanteroexternal andposteromedialmarginsofthefirsttofourthgillarches;
the small anterior fenestra between the cleithrum and coracoid in adults; the high
number of supraneurals (7-8); the similar number ofprecaudal and caudal vertebrae;
and the naked isthmus.
Etymology. Nans is alatin wordthatmeans swimmerin allusion to the habit of
the new genus specimens ofliving in torrents. Gendermasculine.
Nans indefessus sp. n. Figs 1-6, Table 1
Holotype. CI-FML4000, male,49.4mm SL,Argentina, Salta, Orân, rio Bermejobasin,
rio Pescado at Estancia Anta Muerta (22°54.3' S - 64°28.2' W); coll. Mirande, Aguilera &
Padilla,August5, 2003.
Paratypes.AI 107, 1 ex.C&S,42.8mmSL;AI 138, 1 ex.,41.6mmSL,Argentina,Salta,
Orân, rioAnta Muerta tributary ofrio Blanco; coll. Mirande, Aguilera & Ferro, May 2002. AI
mm
157, 3 ex., 39.7-51.7 SL,Argentina, Salta, Orân, arroyo Colorado, tributary ofrio Blanco;
coll. Mirande,Aguilera & Ferro, May 2002. CI-FML4001, 4 ex., 32.0-41.1 mm SL; MNHNG
2643.87, 6ex., 31.5-40.9mm SL; MCNi 911, 2ex., 30.1-33.2mmSL, collectedwiththe holo-
type. CI-FML 4002, 1 ex., 28.4 mm SL, Argentina, Salta, Orân, El Oculto, rio Blanco; coll.
Mirande,Aguilera & Quoirin, October 2001. CI-FML4003, 3 ex., 41.6-44.5 mm SL, rioAnta
Muerta, tributary ofrioBlanco; coll. Mirande,Aguilera& Ferro, May 2002.
718 J- M. MIRANDEETAL.
Diagnosis. As forthe genus.
Description. Morphometries ofholotypeand 18 paratypesarepresentedintable
1. Body subcircularin cross section, more laterally compressedposteriorly; maximum
body depth just anterior to dorsal-fin insertion. Dorsal profile of body straight or
scarcely convex between snout and dorsal-fin origin; straight posterior ofbase ofthat
fin. Dorsal andventral profiles ofcaudalpeduncle straightorventral scarcely concave.
Ventral profile from lowerjaw to pelvic-fin origin convex, almost straight or slightly
convex between pelvic and anal-fin insertions, slightly convex above anal-fin base in
females andjuveniles, markedly so in males; abruptly slanted dorsally, especially in
males.
Table 1. Nans indefessus gen. n., sp. n. Morphometries of male holotype and 18 paratypes.
Minimum, maximum, and mean± standarddeviation inbrackets. SLis measuredin mm.
Holotype Females (n=9) Males (n=10)
SL 49.4 28.4-51.7 31.5-49.4
%
ofstandard length
Predorsal distance 51.4 52.0-57.7 (53.9+1.9) 51.0-53.2 (52.0±0.9)
Preanal distance 63.6 63.4-71.2 (66.1±2.6) 62.1-67.4 (64.4±1.7)
Prepectoraldistance 19.2 16.0-20.5 (18.4+1.6) 16.9-20.5 (18.4+1.1)
Body depth 31.7 27.5-32.1 (29.5±1.6) 28.7-33.3 (30.6±1.4)
Dorsal-finbase 13.2 11.1-12.9 (11.8+0.6) 11.8-13.3 (12.6+0.6)
Anal-finbase 18.2 14.1-19.8 (16.8+1.6) 15.7-19.5 (17.5+1.2)
Pectoral-fin length 23.3 21.4-23.4 (22.4±0.7) 22.6-25.5 (24.2±0.9)
Pelvic-fin length 16.3 14.4-15.6 (15.0±0.5) 15.0-18.0 (16.6±0.8)
Pectoral-pelvic fin origins 26.0 25.6-30.6 (27.6±1.7) 23.4-27.5 (26.1+1.2)
Pelvic-anal finorigins 19.2 16.0-20.5 (18.4+1.6) 16.9-20.5 (18.4+1,1)
Head length 26.8 24.7-28.7 (27.1+1.4) 25.8-30.4 (27.5±1.4)
Peduncle depth 13.8 12.3-14.6 (13.3±0.7) 12.6-14.4 (13.5±0.6)
Peduncle length 24.6 20.5-22.8 (21.4±0.9) 20.6-24.6 (22.4±1.4)
%
ofhead length
Snout length 23.2 19.3-25.1 (22.6±2.1) 19.7-23.5 (21.8+1.4)
Orbital diameter 27.8 28.5-34.4 (30.4±2.2) 25.5-33.6 (29.7±2.7)
Interorbital width 29.3 27.0-30.4 (28.9+1.2) 26.6-30.6 (28.3+1.1)
Maxillary length 24.4 20.6-25.4 (22.7±1.5) 18.9-26.7 (22.9±2.5)
Premaxillary+max. length 36.5 36.9-39.6 (38.0±0.9) 32.4-40.9 (38.3±2.6)
Postorbital length 50.7 46.9-58.4 (50.5±3.9) 44.7-52.7 (49.0±2.6)
Dorsal-fin origin situated almost equidistant from snout and caudal-fin base.
Small adipose fin located posterior to vertical through base ofposterior most anal-fin
ray. Pelvic-fininsertionlightly anteriortoverticalthroughdorsal-fininsertion.Anal-fin
originlocatedatavertical throughbase ofposteriormostdorsalfin. Pectoralandpelvic
fins short, not reaching vertical through pelvic fin insertion or anal-fin origin respec-
tively.
Dorsal fin with ii,7-8 rays (7 in 2 ex. including holotype, 8 in 16 ex.); posterior
margin rounded, bearing first two or three branched rays longest. Anal fin with iii-
iv,10-15 rays (10 in 1 ex., 11 in 4 ex. including holotype, 12 in 7 ex., 5 in 5 ex., 14 in
1 ex., 15 in 1 ex.). Firstbranched anal-finrays longest, theirlengthequalto orscarcely
longer than base of anal fin. Distal margin of anal fin straight more so in males, and
very slightly concave in females. Hooks on anal fin absent.
NEWGENUSAND SPECIES OFCHARACIDAE 719
Fig. 1
mm
Nans indefessusgen. n. and sp. n., holotype,49.4 SL, male.
Caudal fin emarginate, with lower lobe slightly broader and longer than upper
lobe. Caudal-finraysnumbers variable(10+6branchedand 1 unbranchedraysinlower
lobe in 1 ex., 10+7 branched and 1 unbranched rays in lower lobe in 1 ex., 9+7
branched and 1 unbranched rays in lower lobe in 1 ex., 10+8 branched and 1 un-
branched rays in lower lobe in 16 ex. including holotype).
Pectoral fin with i,10-13 rays (10 in 5 ex., 11 in 10 ex. including holotype, 12
in3 ex., 13 in 1 ex.). Distal margin offinrounded. Pelvic finwithpelvic splint andi,7-
8 rays (7 in 17 ex. including holotype, 8 in 2 ex.). Males with strong hooks on all
branched pelvic-fin rays, even in smallest specimens (Figs 2, 3). Hooks directed
anteriorly, one per segment even in unbranched portion ofrays, and distributed along
all ray branches.
Dorsal profile of snout strongly convex from snout tip to vertical through
anterior margin ofeye. Head profile slightly convex or straight from that point to top
ofsupraoccipital spine. Mouthterminal, situatedjustundermiddle ofeye. Eyenotably
larger than snout. Infraorbitals reduced in size, with ventral margins distant from pre-
opercular sensory canal, leaving a wide area ofunderlying musculature covered only
by skin.
Premaxilla with acute ascending process and short alveolar ramus. Premaxilla
bearing two series ofteeth; external row with teeth shorterthan those ofposteriorrow.
Outertooth series with 2(1 ex.), 3 (13 ex. including holotype), or4 (5 ex.) teeth; teeth
anteroposterior^ compressed only distally. Inner premaxillary tooth series with 5
conical teeth, compressed only distally, bearing three cusps. Fifth tooth smaller, and
slightly posterior to proximate tooth. Maxilla with slender dorsal process and long,
relatively narrow, laminar process. Maxilla with 4 (10 ex.), 5 (8 ex.), or 6 (1 ex.)
tricuspid, slender, and distally compressedteeth. Dentary bearing 8-10 slightly conical
teeth, compressed only distally, with one to three cusps; first four teeth larger, with
following teeth smaller.
720 J- M- MIRANDEETAL.
Fig. 2
Nans indefessusgen. n. and sp. n., ventral view ofrightpelvic girdle. Scalebar= 1 mm.
Scales cycloid, with anterior margin rounded, and circuii absent in posterior
field. Noradiianteriorlydirected. Perforatedscalesonlateralline36(3 ex.), 37 (8 ex.),
38 (4 ex.), 39 (2 ex. including holotype), 40 (2 ex.). Five (14 ex.) or 6 (5 ex.) scales
betweenlateralline anddorsal-finoriginand4.5 scalesbetweenlateralline andpelvic-
fin origin. Fourteen or 15 scales between supraoccipital tip and dorsal-fin origin.
Thirteen or 14 scales around caudal peduncle. Most specimens with two rows
composed of4-6 scales on anal-fin base, few specimens with 5-6 scales in one row;
scales always covering first 6 anal-fin rays. Few scales on caudal-fin base. Isthmus
naked.
Four cleared and stained specimens with 13 ribs, 35-36 total vertebrae; 7-8
supraneurals; 10-11 dorsal procurrent rays and 9-10 ventral procurrent rays in caudal
fin. Two rows ofossified gill rakers on 1st to 4th branchial arches. First arch with 1-2
gillrakersonhypobranchial, 5-6onceratobranchial, 1 oncartilage, 2-4onepibranchial
along anterolateral margin; and 3-4 rakers on ceratobranchial, 1 on cartilage, 3-4 on
epibranchial along posteromedial margin.
Colorin life. Background silvery, with dorsal portion offlanks darker. Metallic
gold lateral band visible, although faint. Notable black humeral spot, vertically
expanded, narrow. Dorsal, anal, andcaudal fins lightpinktointensered.Anteriormost
dorsal and anal-fin rays white.
Color in alcohol. Background yellowish. Upper part of flanks with chroma-
tophores forming light, reticulate pattern. Uniformly wide lateral band light grey,
beginning close to humeral spot and ending on middle of caudal peduncle. Grey
humeral spotvertically-expanded, extending fromhorizontalthrough dorsal margin of
orbital, to horizontal through ventral margin ofpreopercle. Humeral spot very narrow
in many specimens.
Dorsal fin with numerous chromatophores on membranes, forming a diffuse
spot, occupying basal two thirds of fin. Anal fin with scattered chromatophores on
membranes. Adipose, caudal, pectoral and pelvic fins hyaline.
Dark narrow line on dorsal portion ofbody between supraoccipital and caudal
peduncle. Dorsal portion of head grey. Few chromatophores present on premaxilla,
maxilla, and around infraorbitals. Chromatophores concentrated and forming two
blackspotsondorsalandventralregionsofeye. Some specimens withchromatophores
concentrated on upperpreopercularprocess and on preopercular articular area.
Sexual dimorphism. The rotation ofthe pelvic bone is present also in females,
although the curvature ofthe pelvic fin is more pronounced in males. In mature males
NEWGENUS AND SPECIES OFCHARACIDAE 721
Fig. 3
Nans indefessusgen. n. and sp. n., detail ofpelvic fin ofone paratype, CI-FML4003, 44.5 mm
SL, male.
bothpelvic finsformatubularstructurewhichisalwaysabsentinfemales.Thefemales
haverelatively longerlengthbetween snouttip andinsertion offirstdorsal-finray, and
also between origins of pectoral and pelvic fins. The males have relatively longer
pectoral and pelvic fins and caudal peduncle.
Etymology. The specific name indefessus is a latin adjective that means un
tiring, in allusion to the high velocity of the water in which the specimens were
collected.
Distribution. The specimens were collected in the rio Anta Muerta and arroyo
Colorado, tributaries of the rio Blanco, and in the rio Pescado; all in the upper rio
Bermejo basin, in the province of Salta, Argentina (Fig. 4). The specimens were col-
lectedinareasofthe streams orriverswithgravelbottom, lowdepth, andclear,rapidly
flowing water. Submerged vegetation was scarce.
DISCUSSION
Under the traditional concept of Astyanax (Eigenmann, 1921, 1927), Nans
should be included in that genus because both genera share the premaxilla with five
teethin asecond series, completelateral line, thecaudal finnaked, andabsenceofpre-
dorsal spine. Nonetheless, Nans has many characters that distinguishes it from
Astyanax. The dorsal fin with two unbranched plus seven or eight branched rays is
presentinNans, whereasAstyanaxhasthe dorsal fin withtwo orthreeunbranched and
nine branched rays, considered as the primitive condition of the character. Nans has
722 J. M. MIRANDEETAL.
RioGrande
deTanja
-23£
RioBermejo
40km
Tropicof
Capricorn
RioSan Francisco
i
Fig. 4
Geographicalknown distributionofNans indefessusgen. n. and sp. n. intheupperrio Bermejo
basin, Orân, province ofSalta,Argentina. 1, type locality, noPescado atEstanciaAntaMuerta.
2, rio Anta Muerta, tributary ofrio Blanco. 3, arroyo Colorado, tributary ofrio Blanco. 4, El
Oculto, rio Blanco.
short anal fin with 10-15 branched rays. In contrast,Astyanax has longer anal fin with
more than 18 branched rays, excluded A. brachypterygium, A. cremnobates, and A.
jenynsii (Bertaco & Malabarba, 2001). Nans has the infraorbitals 2 and 3 reduced in
size, with their ventral margins distant from preopercular sensory canal; the ventral
marginsofthe infraorbitals 2 and3 are situatedveryneartopreopercularsensorycanal
inAstyanax, this is the common condition among characids. Also, Nans has the ante-
riorportion ofbody subcircularin cross section andAstyanaxhas thatportion ofbody
laterallycompressed. InNans, the gillrakers onfirstceratobranchial are short, conical,
andlocatedin two rows whereasAstyanaxhas long, setiformgill rakers locatedin one
row. The scales ofNans have rounded anterior margin (vs. straight inAstyanax). The
isthmus is naked in Nans and it is covered with scales inAstyanax. The premaxillary
anddentaryteethofNansareconicalalthoughtheirdistaltips arecompressedandbear
three cusps; in Astyanax, premaxillary and dentary teeth have broad crowns with
NEWGENUSAND SPECIES OFCHARACIDAE 723
Fig. 5
Nans indefessus gen. n. and sp. n., right anterolateral view of snout bones. Olfactory foramen
partially boundedby cartilage; a large foramen placed in dorsomedial vomerine lamellafor ar-
ticulation with mesethmoid. Scalebar= 1 mm.
denticulated free margin. The dorsal margin ofdentary between coronoid process and
symphysis abruptly tapers ventrally in Nans, ressembling that of Bryconamericus,
whereas the same margin is almost straight in the dentary ofAstyanax. Many osteo-
logical characters differentiate Nans from Astyanax: blunt sphenotic spine (vs. long
sphenotic spine in Astyanax); very short supraoccipital spine (vs. relatively long);
sevenoreight supraneurals (vs. fourto six); largeorbitosphenoidwithits anteraventral
marginnearparasphenoid (vs. shortorbitosphenoid); slenderpostcleithrum3 (vs. post-
cleithrum 3 with laminar portion); the short nasals do not surpass the lateral wings of
mesethmoid (vs. long nasals, surpassing the lateral wings of mesethmoid); the
olfactory foramen is partially bounded by cartilage in Nans whereas it is completely
bounded by bone in Astyanax. The latter and other characters present in Nans are
discussed below.
724 J- M. MIRANDEETAL.
FlG. 6
Nans ìndefessus gen. n. and sp. n., left lateral view of extrascapula, postemporal and supra-
cleithrum. Sensory canals developed on extrascapula and supracleithrum; a sensory canal is
absentonpostemporal. Scale bar= 1 mm.
The new genus lacks the synapomorphies of phylogenetically defined sub-
families or genera, such as the Glandulocaudinae (Weitzman & Fink, 1985; Weitzman
etal, 1994; Weitzman & Ortega, 1995; Weitzman & Menezes, 1998), Cheirodontinae
(Malabarba, 1998), Stethaprioninae (Reis, 1989), Serrasalminae (Machado Allison,
1983), and the genera Moojenichthys (Castro & Vari, 1990), Hypobrycon (Malabarba
& &
Malabarba, 1994), Jupiaba (Zanata, 1997), Attonitus (Vari Ortega, 2000),
Caiapobrycon (Malabarba & Vari, 2000), Creagrutus and Piabina (Vari & Harold,
2001), and Deuterodon (Lucena & Lucena, 2002).
The following characters are pertinent to the question of the phylogenetic
placement ofthe new genus:
1- The presence ofii,7-8 dorsal fin rays in Nans, separates it from most genera
of characids. Recently, Malabarba & Weitzman (2003) published the description of
Cyanocharax, including the phylogenetic diagnosis of a putative clade A which is
diagnosed by the presence ofii,8 dorsal-fin rays and 4 teeth in the inner premaxillary
row. The first synapomorphy is present in Nans which, however, always have 5 pre-
maxillary teethinthe innerrow. Furthermore, the terminal mouthofNansdistinguishes
itfromgeneraincludedin cladeA, all ofwhich have ventrally-locatedmouths, ormod-
ified teeth. The genus Cyanocharax, with terminal mouth and generalized teeth, has 6
branched pelvic-fin rays in contrast to the pelvic fin ofNans with 7-8 branched rays.
Modificationsrelatedto sexual dimorphismare often found in characids. Males
ofdifferent genera ofGlandulocaudinae (Weitzman & Fink, 1983; Weitzman & Fink,
1985; Menezes & Weitzman, 1990), Cheirodontinae (Malabarba, 1998), and many
tetragonopterins have hooks variably present on the anal and pelvic fins; some
tetragonopterins also have hooks on pectoral, caudal, and/ordorsal fins. Modifications
ofthe pelvic girdle such as those present in Jupiaba (Zanata, 1997), are uncommon in
characids. Nans has three possibly autapomorphic characters related to the pelvic
girdle, and pelvic muscles.
2- In most characids, the pelvic bone is located in a horizontal plane. In males
and females ofNans, the pelvic bone is positioned in a vertical plane, with the primi-
tively external, posterolateral margin ofthe bone shifted ventrally (Fig. 2).
3-Thepelvic fishmuscles are usuallylocatedonthe dorsal andventral surfaces
of the pelvic bone (Winterbottom, 1974; Zanata, 1997). As a consequence of the